Ion drag pumps



E. BENZ ION DRAG PUMPS May 19, 1964 Filed May 15, 1962 FIG. 2

INVENTOR.

EMIL BENZ ATTORNEY United States Patent Ofiice 3,133,500 Patented May 19, 1964 3,133,500 ION DRAG PUMPS Emil Benz, St. Paul, Minn, assignor, by mesne assignments, to Litton Systems, Inc., Beverly Hills, Calif., a corporation of Maryland Filed May 15, 1962, Ser. No. 194,832 9 Claims. (Cl. 103-1) This invention relates to pumps, and, more particularly,

to pumps having no moving parts and being especiallysuited for continuously pumping insulating liquids.

It is known that insulating liquids can be pumped using the principles of ion drag. One pump based on those principles is described in a paper by Otmar M. Stuetzer entitled Ion Drag Pump, published in the Journal of Applied Physics, volume 31, Number 1, 136-146, January 1960. Ion drag pumps are based on the effect that, when ions in a perfectly ionized medium move under the influence of an electric field, friction with the carrier medium transfers momentum to the latter. If ions of only one polarity are present, appreciable pressure may be created by this means.

Applying ion drag principles to a pump for insulating liquids involves increasing the concentration of ions present in the liquid. The increased concentration of ions is accelerated by an electric field and under its effect the ions move in one relative direction. As they move, the ions frictionally engage molecules of the insulating liquid and drag them in a direction approximately parallel to the lines of force of the electric field. Thus, momentum and movement are imparted to the liquid and it is, in effect, pumped.

The means for increasing the concentration of ions in the liquid and causing the ions to move under the influence of an electric field generally comprises one or more emitter electrodes and one or more collector electrodes, with a source of high potential connected between the emitter and collector electrodes. The present invention is directed toward providing an improved ion drag pump which embodies a plurality of emitter electrodes cooperating with a single collector electrode to provide a plurality of pumping stages.

Heretofore, ion drag pumps have generally employed a pointed emitter electrode arranged opposite a small opening in a collector electrode. in a device requiring a flow rate greater than that available from a single point emitter electrode, several points have been mounted in parallel. Also, if a greater pumping pressure was required than was available from a single point electrode or from a multiple point electrode structure with the electrodes conected in parallel, several pumping stages have been arranged in series.

Either the parallel arrangement or the series arrangement may be difiicult to manufacture, particularly when a considerable number of points or stages are desired. Such arrangements tend to become bulky and, therefore, heavy, and electrical connections to the various electrodes or stages may be difficult to make. The present invention provides an ion drag pump which embodies both parallel and series arrangements of pumping electrodes, and which is characterized by case of manufacture, small size and light weight, and simplicitiy of electrical connections.

Broadly speaking, the present invention provides an ion drag pump for insulating liquids, which comprises two concentrically arranged conduits. The inner conduit extends iuto the outer conduit with the end of the inner conduit being closed and the end of the outer conduit through which the inner conduit extends being closed about the inner conduit. The inner conduit has a plurality of apertures radially arranged in one or more planes normal to the axis of the conduits, and an equal plurality of corona discharge points extend inwardly through the outer conduit. The corona discharge points are radially arranged in the planes with each corona point substantially opposite an aperture. Of course, electrical means are connected between the inner conduit and the corona discharge points for establishing ionization and high field strength in the insulating liquid between the inner conduit and the corona points.

The invention will be better understood by reference to the following description of a preferred embodiment, taken in conjunction with the accompanying drawing, in which FIGURE 1 is a diagrammatic sectional view of an ion drag pump constructed according to the teachings of the invention; and

FIGURE 2 is a sectional view taken on the line 22 of FIGURE 1.

As used herein, the term insulating liquid includes both those liquids that are truly insulating and those that are poorly conducting. Examples of such liquids are lubricating oil, machine oil, silicone oil, castor oil, octane and kerosene, to name but a few.

In the illustrated embodiment of the pump of the invention, a flow path for the insulating liquid to be pumped is defined by an outer conduit 10, which may or may not be made of an electrically conductive material, and by an inner conduit 11 made of an electrically conductive material. The conduits 1t) and 11 are preferably cylindrical and are concentrically arranged with the inner conduit 10 extending into the outer conduit 11. The lower end 11a of the inner conduit is closed, and the upper end of the conduit 10 through which the inner conduit 11 extends is closed about the inner conduit by means of conventional sealing means, such as an insulating collar '12. An entry conduit or pipe 13 may be secured to the lower end of the outer conduit 10, and an exit conduit or pipe 14 may be secured to the upper end of the inner conduit 11.

The inner conduit 11, which serves as the collector electrode for the ion drag pump, is provide-d with a plurality of apertures 11!) through its side wall. The appertures 11b are radially arranged in a series of planes normal to the axes of the conduits 10 and '11. Preferably, the apertures 11b are substantially circular in shape, are of equal diameter, and are evenly spaced about the circumference of the conduit 11. The various planes containing the apertures 11b are evenly spaced apart along the axis of the conduit, and the apertures lie on the same radii in each of the planes to provide axial alignment of the apertures.

A plurality of corona discharge points 15 extend inwardly through openings in the outer conduit 10, and are radially arranged in the same planes as the apertures 1 1b with a corona discharge point substantially opposite each aperture. The corona discharge points 15 are preferably of such length that the tip of each point is spaced from its corresponding aperture 1111 by a distance substantially equal to the diameter of the aperture.

In the illustrated embodiment of the invention, the outer conduit 10 is made of a conductive material, so that when it is connected to one side of a potential source 16 through a current-limiting resistor 17, all of the corona discharge points 15 are electrically connected in parallel to the source 16. Of course, if the outer conduit 10 is made of a non-conductive material, the corona discharge points 15 may be individually connected in parallel to the potential source 16.

In operation, when the inner and outer conduits are connected to the voltage source, a high strength electric field is established between the corona discharge points 15 and the inner conduit 11. With the formation of that electric field, the concentration of ions in the insulating liquid in the vicinity of the corona discharge points is increased. The ions thus formed are accelerated by the electric field and under its effect move toward and through the apertures in the inner conduit 11, which functions as a collector electrode. As they move, these ions engage molecules of the insulating liquid and, due to friction between the ions and the molecules, the molecules are dragged toward the inner conduit and through the apertures 1112. Thus, momentum and movement are imparted to the insulating liquid in the direction shown by the arrows (upwardly). The theory underlying this phenomenon is explained in detail in the above-mentioned technical paper, and therefore, will not be treated extensively here.

In a practical application, the voltage supplied between the corona discharge points and the inner conduit should be sufiicient to induce corona dischange therebetween, but should be less than that which would cause a spark to appear in the particular insulating liquid being pumped. It has been found that 5-15 kv. are generally required to accomplish the desired result. The current limiting resistor 17 should be of a value to limit current flow to the order of 1000 microamperes or less.

it will be seen that the ion drag pump of the present invention actually provides a plurality of pumps, some of which operate hydrodynamically in parallel, with groups of parallel pumps operating hydrodynamically in series 'with each other. in other words, all of the pumps lying in any one plane, each comprising a corona discharge point 15 and an aperture 111), are hydrodynamically in parallel; the planes, each plane containing a plurality of pumps, are hydrodynamically in series with each other in the direction of flow of the insulating liquid. Although the embodiment illustrated contains ten planes with each containing eight pumps, the invention is in no way limited to the use of any particular number of pumps or any particular number of planes. The choice of the number of pumps and their arrangement in the various planes is controlled by the required rate of flow and pressure of the particular application involved.

It is pointed out that the apertures 11b in the inner conduit 11 and the openings in the outer conduit 15) through which the corona discharge points 15 extend must be very carefully aligned. This operation may be conveniently done on a milling machine using a dividing head.

While the sealing means 12 which position the inner conduit 11 with respect to the outer conduit is being formed and secured, the inner conduit may be held in the center of the outer conduit by means of pins. The pins may be pushed through the openings from side to side of the outer conduit and through the inner conduit, thus aligning the two conduits coaxially. After the seal is completed, the pins may be removed and the corona discharge points inserted through their openings and soldered into the outer conduit.

An ion drag pump constructed in accordance with the teachings of the present invention has numerous advantages over those pumps heretofore known. For example, it is simple to manufacture and a large number of pumping stages may be incorporated into the embodiment without unduly complicating the process of manufacture. It is smaller in size for a given number of corona discharge points and, consequently, is lighter in weight than previous devices embodying a like number of points. Because the outer conduit may be made of a conductive material, it is simple to connect electrically with only two leads being required. Furthermore, it is completely symmetrical with respect to the direction of pumping so that maximum effect may be obtained from each pumping stage.

Although a specific embodiment of the invention has been shown and described, it is apparent that many modifications may be made by one skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. An ion drag pump for pumping an insulating liquid comprising a conductive iimer conduit and an outer conduit defining a flow path for said liquid, said conduits being concentrically arranged with said inner conduit extending into said outer conduit, the end of said inner conduit inside said outer conduit being closed and the end of said outer conduit through which said inner conduit extends being closed about said inner conduit, said inner conduit having a plurality of apertures radially arranged in a plane normal to the axis of said conduits, an equal plurality of corona discharge points extending inwardly through said outer conduit and radially arranged in said plane with a corona point substantially opposite each said aperture, and means connected between said inner conduit and said corona discharge points for establishing ionization and high field strength in said insulating liquid between said conora points and said inner conduit.

2. The ion drag pump defined by claim 1, wherein said A apertures are substantially circular of equal diameter and evenly spaced about the circumference of said inner conduit.

3. The ion drag pump defined by claim 2 wherein the spacing between the tips of said corona points and said apertures is substantially equal to the diameter of said apertures.

4. An ion drag pump for pumping an insulating liquid 7 comprising a conductive inner conduit and an outer conduit defining a flow path or said liquid, said conduits being concentrically arranged with said inner conduit extending into said outer conduit, the end of said inner con- ,duit inside said outer conduit being closed and the end of said outer conduit through which said inner conduit extends being closed about said inner conduit, said inner conduit having a plurality of apertures radially arranged in planes normal to the axis of said conduits, an equal plurality of corona discharge points extending inwardly through said outer conduit and radially arranged in said planes with a corona discharge point substantially opposite each said aperture, and means connected between said inner conduit and said corona discharge points for establishing ionization and high field strength in said insulating liquid between said corona points and said inner conduit.

5. The ion drag pump defined by claim 4, wherein all said planes contain equal numbers of said apertures and corona discharge points.

6. The ion drag pump defined by claim 4 wherein said apertures are substantially circular of equal diameter and evenly spaced about the circumference of said inner conduit.

7. The ion drag pump defined by claim 5, wherein said planes are evenly spaced apart along the axis of said conduits.

8. The ion drag pump defined by claim 6, wherein the spacing between the tips of said corona points and said apertures is substantially equal to the diameter of said apertures.

9. The ion drag pump defined by claim 7, wherein the apertures lie on the same radii in each of said planes to provide axial alignment.

References Cited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS France Oct. 10, 1960 

1. AN ION DRAG PUMP FOR PUMPING AN INSULATING LIQUID COMPRISING A CONDUCTIVE INNER CONDUIT AND AN OUTER CONDUIT DEFINING A FLOW PATH FOR SAID LIQUID, SAID CONDUITS BEING CONCENTRICALLY ARRANGED WITH SAID INNER CONDUIT EXTENDING INTO SAID OUTER CONDUIT, THE END OF SAID INNER CONDUIT INSIDE SAID OUTER CONDUIT BEING CLOSED AND THE END OF SAID OUTER CONDUIT THROUGH WHICH SAID INNER CONDUIT EXTENDS BEING CLOSED ABOUT SAID INNER CONDUIT, SAID INNER CONDUIT HAVING A PLURALITY OF APERTURES RADIALLY ARRANGED IN A PLANE NORMAL TO THE AXIS OF SAID CONDUITS, AN EQUAL PLURALITY OF CORONA DISCHARGE POINTS EXTENDING INWARDLY THROUGH SAID OUTER CONDUIT AND RADIALLY ARRANGED IN SAID PLANE WITH A CORONA POINT SUBSTANTIALLY OPPOSITE EACH SAID APERTURE, AND MEANS CONNECTED BETWEEN SAID INNER CONDUIT AND SAID CORONA DISCHARGE POINTS FOR ESTABLISHING IONIZATION AND HIGH FIELD STRENGTH IN SAID INSULATING LIQUID BETWEEN SAID CONORA POINTS AND SAID INNER CONDUIT. 